• Restorative Dentistry and Endodontics
• /
• v.33 no.3
• /
• pp.246-257
• /
• 2008

The purpose of this study was to investigate the influence of various occlusal loading sites and directions on the stress distribution of the cervical composite resin restorations of maxillary second premolar, using 3 dimensional (3D) finite element (FE) analysis. Extracted maxillary second premolar was scanned serially with Micro-CT (SkyScan1072; SkyScan, Aartselaar, Belgium). The 3D images were processed by 3D-DOCTOR (Able Software Co., Lexington, MA, USA). HyperMesh (Altair Engineering, Inc., Troy, USA) and ANSYS (Swanson Analysis Systems, Inc., Houston, USA) was used to mesh and analyze 3D FE model. Notch shaped cavity was filled with hybrid (Z100, 3M Dental Products, St. Paul, MN, USA) or flowable resin (Tetric Flow, Vivadent Ets., FL-9494-Schaan, Liechtenstein) and each restoration was simulated with adhesive layer thickness ($40{\mu}m$). A static load of 200 N was applied on the three points of the buccal incline of the palatal cusp and oriented in $20^{\circ}$ increments, from vertical (long axis of the tooth) to oblique $40^{\circ}$ direction towards the buccal. The maximum principal stresses in the occlusal and cervical cavosurface margin and vertical section of buccal surfaces of notch-shaped class V cavity were analyzed using ANSYS. As the angle of loading direction increased, tensile stress increased. Loading site had little effect on it. Under same loading condition, Tetric Flow showed relatively lower stress than Z100 overall, except both point angles. Loading direction and the elastic modulus of restorative material seem to be important factor on the cervical restoration.

• Journal of Korean Port Research
• /
• v.12 no.1
• /
• pp.35-46
• /
• 1998

The CY can be said to function in various respect as a buffer zone between the maritime and overland inflow-outflow of container. The amount of storage area needed requires a very critical appraisal at pre-operational stage. A container terminal should be designed to handle and store containers in the most efficient and economic way possible. In order to achieve this aim it is necessary to figure out or forecast numbers and types of containers to be handled, CY area required, and internal handling systems to be adopted. This paper aims to calculate the CY area required for each container handling system in Mokpo New Port. The CY area required are directly dependent on the equipment being used and the storage demand. And also the CY area required depends on the dwell time. Furthermore, containers need to be segregated by destination, weight, class, FCL(full container load), LCL(less than container load), direction of travel, and sometimes by type and often by shipping line or service. Thus the full use of a storage area is not always possible as major unbalances and fluctuations in these flow occuring all the time. The calculating CY area must therefore be taken into account in terms of these operational factors. For solving such problem, all these factors have been applied to estimation of CY area in Mokpo New Port. The CY area required in Mokpo New Port was summarized in the conclusion section.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.19 no.4
• /
• pp.332-340
• /
• 2016

Sunken ships cause damage to the environment due to the dispersal of fuel oil and harmful cargo goods in the hull. Since the sunken ship is mostly flooded by the seabed, it tends to be in a relatively stable condition. However, the heavy body, together with the load of remaining goods in the cargo hold, the constant contact with the seabed, and ocean currents and tidal waves, can affect dispersal of residual fuel oils out of the sunken ship. Corrosion of the sunken ship starts upon sinking, decreasing the thickness of the hull structure and sub-materials. Therefore, it is necessary to assess the structural stability against the potential breakdown of the sunken ship. Whilst evaluating the danger of the sunken ship, this result should be reflected in 'the possible discharge'. This study was undertaken to suggest a procedure for a step by step evaluation to assess the structural stability a sunken ship. The structural stability assessment to estimate the collapsibility of the hull was structure targeted at the sunken ship 'No. 7 HaeSung', which was classified as the prime example for the intensive management of sunken ships. This study was undertaken to suggest a procedure for a step by step evaluation to assess the structural stability a sunken ship and to propose a method to conduct a structural safety assessment that estimates the collapsibility of the hull by targeting the sunken ship 'No. 7 HaeSung',which was classified as the prime example for the intensive management of sunken ships. The collapsibility of the hull structure was estimated Based on the damage size of the hull structure, and the corrosion rate of the hull structure and sub-materials due to the seawater after sinking. It was confirmed that there was a low possibility of the total destruction of the hull structure at the current time. However, there is a high possibility in the potential failure of the hull structure due to increased rate of corrosion thereafter. Therefore, we believe continuous study on influence of corrosion and marine environment change to sunken ship's structural safety is necessary.

• The Journal of Korean Academy of Prosthodontics
• /
• v.46 no.3
• /
• pp.290-297
• /
• 2008

STATEMENT OF PROBLEM: Implant-supported fixed cantilever prostheses are influenced by various biomechanical factors. The information that shows the effect of implant number and position of cantilever on stress in the supporting bone is limited. PURPOSE: The purpose of this study was to investigate the effect of implant number variation and the effect of 2 different cantilever types on stress distribution in the supporting bone, using 3-dimensional finite element analysis. MATERIAL AND METHODS: A 3-D FE model of a mandibular section of bone with a missing second premolar, first molar, and second molar was developed. $4.1{\times}10$ mm screw-type dental implant was selected. 4.0 mm height solid abutments were fixed over all implant fixtures. Type III gold alloy was selected for implant-supported fixed prostheses. For mesial cantilever test, model 1-1 which has three $4.1{\times}10$ mm implants and fixed prosthesis with no pontic, model 1-2 which has two $4.1{\times}10$ mm implants and fixed prosthesis with a central pontic and model 1-3 which has two $4.1{\times}10$ mm implants and fixed prosthesis with mesial cantilever were simulated. And then, 155N oblique force was applied to the buccal cusp of second premolar. For distal cantilever test, model 2-1 which has three $4.1{\times}10$ mm implants and fixed prosthesis with no pontic, model 2-2 which has two $4.1{\times}10$ mm implants and fixed prosthesis with a central pontic and model 2-3 which has two $4.1{\times}10$ mm implants and fixed prosthesis with distal cantilever were simulated. And then, 206N oblique force was applied to the buccal cusp of second premolar. The implant and superstructure were simulated in finite element software(Pro/Engineer wildfire 2.0). The stress values were observed with the maximum von Mises stresses. RESULTS: Among the models without a cantilever, model 1-1 and 2-1 which had three implants, showed lower stress than model 1-2 and 2-2 which had two implants. Although model 2-1 was applied with 206N, it showed lower stress than model 1-2 which was applied with 155N. In models that implant positions of models were same, the amount of applied occlusal load largely influenced the maximum von Mises stress. Model 1-1, 1-2 and 1-3, which were loaded with 155N, showed less stress than corresponding model 2-1, 2-2 and 2- 3 which were loaded with 206N. For the same number of implants, the existence of a cantilever induced the obvious increase of maximum stress. Model 1-3 and 2-3 which had a cantilever, showed much higher stress than the others which had no cantilever. In all models, the von Mises stresses were concentrated at the cortical bone around the cervical region of the implants. Meanwhile, in model 1-1, 1-2 and 1-3, which were loaded on second premolar position, the first premolar participated in stress distribution. First premolars of model 2-1, 2-2 and 2-3 did not participate in stress distribution. CONCLUSION: 1. The more implants supported, the less stress was induced, regardless of applied occlusal loads. 2. The maximum von Mises stress in the bone of the implant-supported three unit fixed dental prosthesis with a mesial cantilever was 1.38 times that with a central pontic. The maximum von Mises stress in the bone of the implant-supported three-unit fixed dental prosthesis with a distal cantilever was 1.59 times that with a central pontic. 3. A distal cantilever induced larger stress in the bone than a mesial cantilever. 4. A adjacent tooth which contacts implant-supported fixed prosthesis participated in the stress distribution.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.15 no.6
• /
• pp.135-146
• /
• 2011

Steel structures have been generally painted to prevent corrosion damage. However, the painted film is deteriorated with increase in service life, and then corrosion damage resulting in cross sectional area occurs on steel surface. As a result, the buckling strength of steel structures can be decreased due to the corrosion damages. The evaluation method of the axial buckling strength of columns about a variety of section shapes and supporting conditions have been presented, but evaluation method of buckling strength about irregular nonprismatic columns is not established. In this study, the axial buckling strength of corroded steels was evaluated based on the buckling test results of corroded steel specimens that were cut off at a temporary steel structure. The corroded specimens were picked up total 10 specimens according to various slenderness ratio from the web of a temporary structure's main beam. The length of specimens is 200, 300, 400, 500 and 600mm respectively. The rust productions were removed by the chemical treatment. Then, the surface geometry was measured at intervals of $1{\times}1mm$ by using the optical 3D digitizing system, and the residual thickness of the specimens was calculated. The axial buckling test was performed on 10 corroded specimens and 12 non-corroded specimens under the fixed-fixed support condition. From the test results, the effect of corrosion damages on axial buckling load was investigated. Regardless of corrosion damage degree, the axial buckling strength of corroded specimens and non-corroded specimens was evaluated identically by using minimum average residual thickness or average residual thickness to minus its standard deviation. Reasonable measuring intervals of residual thickness was proposed by using the results to apply for practical works.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2015.05a
• /
• pp.237-237
• /
• 2015

The district of Marlborough has had more than its share of river management projects over the past 150 years, each one uniquely affecting the geomorphology and flood hazard of the Wairau Plains. A major early project was to block the Opawa distributary channel at Conders Bend. The Opawa distributary channel took a third and more of Wairau River floodwaters and was a major increasing threat to Blenheim. The blocking of the Opawa required the Wairau and Lower Wairau rivers to carry greater flood flows more often. Consequently the Lower Wairau River was breaking out of its stopbanks approximately every seven years. The idea of diverting flood waters at Tuamarina by providing a direct diversion to the sea through the beach ridges was conceptualised back around the 1920s however, limits on resources and machinery meant the mission of excavating this diversion didn't become feasible until the 1960s. In 1964 a 10 m wide pilot channel was cut from the sea to Tuamarina with an initial capacity of $700m^3/s$. It was expected that floods would eventually scour this 'Wairau Diversion' to its design channel width of 150 m. This did take many more years than initially thought but after approximately 50 years with a little mechanical assistance the Wairau Diversion reached an adequate capacity. Using the power of the river to erode the channel out to its design width and depth was a brilliant idea that saved many thousands of dollars in construction costs and it is somewhat ironic that it is that very same concept that is now being used to deal with the aggradation problem that the Wairau Diversion has caused. The introduction of the Wairau Diversion did provide some flood relief to the lower reaches of the river but unfortunately as the Diversion channel was eroding and enlarging the Lower Wairau River was aggrading and reducing in capacity due to its inability to pass its sediment load with reduced flood flows. It is estimated that approximately $2,000,000m^3$ of sediment was deposited on the bed of the Lower Wairau River in the time between the Diversion's introduction in 1964 and 2010, raising the Lower Wairau's bed upwards of 1.5m in some locations. A numerical morphological model (MIKE-11 ST) was used to assess a number of options which led to the decision and resource consent to construct an erodible (fuse plug) bank at the head of the Wairau Diversion to divert more frequent scouring-flows ($+400m^3/s$)down the Lower Wairau River. Full control gates were ruled out on the grounds of expense. The initial construction of the erodible bank followed in late 2009 with the bank's level at the fuse location set to overtop and begin washing out at a combined Wairau flow of $1,400m^3/s$ which avoids berm flooding in the Lower Wairau. In the three years since the erodible bank was first constructed the Wairau River has sustained 14 events with recorded flows at Tuamarina above $1,000m^3/s$ and three of events in excess of $2,500m^3/s$. These freshes and floods have resulted in washout and rebuild of the erodible bank eight times with a combined rebuild expenditure of $80,000. Marlborough District Council's Rivers & Drainage Department maintains a regular monitoring program for the bed of the Lower Wairau River, which consists of recurrently surveying a series of standard cross sections and estimating the mean bed level (MBL) at each section as well as an overall MBL change over time. A survey was carried out just prior to the installation of the erodible bank and another survey was carried out earlier this year. The results from this latest survey show for the first time since construction of the Wairau Diversion the Lower Wairau River is enlarging. It is estimated that the entire bed of the Lower Wairau has eroded down by an overall average of 60 mm since the introduction of the erodible bank which equates to a total volume of $260,000m^3$. At a cost of $$0.30/m^3$ this represents excellent value compared to mechanical dredging which would likely be in excess of $$10/m^3$. This confirms that the idea of using the river to enlarge the channel is again working for the Wairau River system and that in time nature's "excavator" will provide a channel capacity that will continue to meet design requirements.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.26 no.6C
• /
• pp.395-406
• /
• 2006

Drilled shafts are a common foundation solution for large concentrated loads. Such piles are generally constructed by drilling through softer soils into rock and the section of the shaft which is drilled through rock contributes most of the load bearing capacity. Drilled shafts derive their bearing capacity from both shaft and base resistance components. The length and diameter of the rock socket must be sufficient to carry the loads imposed on the pile safely without excessive settlements. The base resistance component can contribute significantly to the ultimate capacity of the pile. However, the shaft resistance is typically mobilized at considerably smaller pile movements than that of the base. In addition, the base response can be adversely affected by any debris that is left in the bottom of the socket. The reliability of base response therefore depends on the use of a construction and inspection technique which leaves the socket free of debris. This may be difficult and costly to achieve, particularly in deep sockets, which are often drilled under water or drilling slurry. As a consequence of these factors, shaft resistance generally dominates pile performance at working loads. The efforts to improve the prediction of drilled shaft performance are therefore primarily concerned with the complex mechanisms of shaft resistance development. The shaft resistance only is concerned in this study. The nature of the interface between the concrete pile shaft and the surrounding rock is critically important to the performance of the pile, and is heavily influenced by the construction practices. In this study, the influences of asperity characteristics such as the heights and angles, the strength characteristics and elastic constants of surrounding rock masses and the depth and length of rock socket, et. al. on the shaft resistance of drilled shafts are investigated from elasto-plastic analyses( FLAC). Through the parametric studies, among the parameters, the vertical stress on the top layer of socket, the height of asperity and cohesion and poison's ratio of rock masses are major influence factors on the unit peak shaft resistance.

• IMMUNE NETWORK
• /
• v.24 no.2
• /
• pp.7.1-7.19
• /
• 2024

Viral load and the duration of viral shedding of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are important determinants of the transmission of coronavirus disease 2019. In this study, we examined the effects of viral doses on the lung and spleen of K18-hACE2 transgenic mice by temporal histological and transcriptional analyses. Approximately, 1×10⁵ plaque-forming units (PFU) of SARS-CoV-2 induced strong host responses in the lungs from 2 days post inoculation (dpi) which did not recover until the mice died, whereas responses to the virus were obvious at 5 days, recovering to the basal state by 14 dpi at 1×10² PFU. Further, flow cytometry showed that number of CD8+ T cells continuously increased in 1×10² PFU-virus-infected lungs from 2 dpi, but not in 1×10⁵ PFU-virus-infected lungs. In spleens, responses to the virus were prominent from 2 dpi, and number of B cells was significantly decreased at 1×10⁵ PFU; however, 1×1² PFU of virus induced very weak responses from 2 dpi which recovered by 10 dpi. Although the defense responses returned to normal and the mice survived, lung histology showed evidence of fibrosis, suggesting sequelae of SARS-CoV-2 infection. Our findings indicate that specific effectors of the immune response in the lung and spleen were either increased or depleted in response to doses of SARS-CoV-2. This study demonstrated that the response of local and systemic immune effectors to a viral infection varies with viral dose, which either exacerbates the severity of the infection or accelerates its elimination.